Stepwise migration: The Strangler-FIG-Pattern for the modernization of old systems

Step by step Migration: The Strangler-Fig-Pattern to Modernize Old Systems

Short: In today's fast-paced digital landscape, many companies face the challenge of modernizing outdated IT systems.

In today's fast-paced digital landscape, many companies face the challenge of modernizing outdated IT systems. These so-called old systems are often the backbone of the company, but their rigid architectures and outdated technologies hinder innovation and growth.

A complete new development is often associated with high costs, risks and long development times. Here, the Altsystem Migration with the Strangler-Fig-Pattern offers an elegant and low-risk alternative.

What is the Strangler-FIG-Pattern?

Short: The Strangler-Fig-Pattern, in German “Würgefeigen-Muster”, is an architectural pattern made popular by Martin Fowler.

The Strangler-Fig-Pattern, in German “Würgefeigen-Muster”, is an architectural pattern made popular by Martin Fowler. The name derives from the wortfeige, a plant that grows on another tree, slowly wraps it around and finally completely replaces it.

Transfer to [software development](/services/software development) this means replacing an old system step by step with a new system by gradually implementing the functionality of the old system in new services and slowly “worn” access to the old system.

Instead of a risky “Big Bang” migration, in which the entire system is replaced at once, the Strangler-Fig-Pattern allows incremental modernization.

A new system is developed parallel to the old one and individual functionalities are gradually migrated from the old system into the new system.

A façade, often in the form of a proxy or api-gateway" class="glossary-link" title="Definition in the IT glossary">API gateway, passes the queries either to the new system or to the old system.

Over time, the new system takes over more and more tasks until the old system can be completely replaced and shut down.

The advantages of gradual migration

Short: The use of the Strangler-FIG-Pattern in the Altsystem Migration offers a number of decisive advantages:

The use of the Strangler-FIG-Pattern in the Altsystem Migration offers a number of decisive advantages:

• Risk minimisation: As migration takes place in small, manageable steps, the risks are drastically reduced compared to a complete new development. Errors and problems can be detected and resolved at an early stage without endangering the entire system.
• Continuous value added: New functionalities and improvements can be quickly switched on, which means that the company continuously benefits from modernization and does not have to wait years for the result. *Slower downtime: Migration can be carried out during operation without long downtime. This is crucial especially for business-critical applications.
• Flexibility: The development team can use modern technologies and architectures for the new system without being bound to the limitations of the old system. This allows the introduction of microservices, cloud-native technologies and agile development

References and further reading

Short: The following independent references complement the topics in this article:

The following independent references complement the topics in this article:

• Bitkom – German digital industry association
• German Federal Office for Information Security (BSI)
• European Commission – Digital strategy
• MDN Web Docs (Mozilla)
• W3C – World Wide Web Consortium

"DevOps is less about tools and more about shared ownership of quality and release discipline."

— Björn Groenewold, Managing Director, Groenewold IT Solutions